The present invention relates to a pneumatic booster usable as a vacuum booster in a brake system of a vehicle, for example.
A brake system of a vehicle generally has a pneumatic booster provided between a brake pedal and a master cylinder. An example of this type of a pneumatic booster is capable of increasing the stroke of a master cylinder-side output rod relative to that of a brake pedal-side input rod in the initial stage of a braking operation. In this pneumatic booster, a rod having a predetermined movable range is interposed between a poppet valve of a valve device and a reaction member, and a part of reaction force from the reaction member is transmitted to the rod to open the poppet valve, thereby increasing the amount of atmospheric air to be introduced into a variable-pressure chamber (for example, see Japanese Patent Application Laid-Open Publication No. 2006-273214).